Individual differences in punished alcohol self-administration are unaltered by alcohol vapor exposure

Continued alcohol use despite negative consequences is a defining feature of alcohol use disorder (AUD). It remains poorly understood whether individual variability in drinking despite negative consequences is due to inherent differences or emerges after prolonged alcohol use. The goal of the present study was to use a rat model of drinking despite negative consequences to assess individual differences in foot shock-punished alcohol self-administration prior to and following alcohol vapor exposure in male Wistar rats. After baseline operant self-administration was established, rats underwent additional self-administration sessions in which random, response-contingent foot shock punishment was introduced. Average percent change from baseline was calculated for each rat during punished sessions and rats were classified into shock-sensitive (SS) and shock-resistant (SR) subgroups using the top and bottom thirds. Rats then underwent 3 cycles of air or alcohol vapor exposure every other week, with unpunished self-administration sessions occurring during the intervening weeks. Following the last vapor cycle, rats were re-assessed for resistance to foot shock during punished self-administration sessions. Alcohol vapor exposure had no effect on punished self-administration overall, nor by subgroup. Examination of individual differences showed that rats classified as SR showed increased unpunished self-administration relative to baseline regardless of air vs. vapor condition. These data suggest that alcohol history has a minimal effect on individual differences in foot shock-punished self-administration.